Plane-landing catapult



Oct.11,1949. V F. JONES 2,484,230

PLANE-LANDING CATAPULT Filed March 8, 1947 JNVER TER IINVENTOR Maurice F Jones.

ATTORN EY Patented Oct. 11, 1949 PLAN E-LANDING CATAPULT Maurice F. Jones, Pittsburgh, Pa., assignor to Westinghouse Electric. Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 8, 1947, Serial N0. 733,286

13 Claims. 1

My invention relates to electric linear-motor catapults, and particularly to control-means for utilizing such catapults for making assisted plane-landings, to reduce the length of the landing-run of an airplane which is landing at a landing-field.

The general type of catapult-equipment to which my invention is related is described and claimed in a patent of Frank B. Powers, 2,404,984, granted July 30, 1946, and also described and claimed in a patent of R. C. Jones, 2,412,514, granted December 10, 1946, a patent of R. C. Jones and myself, 2,412,515, granted December 10, 1946, my Patent 2,428,570, granted October 7, 1947, an application of R. C. Jones, Serial No. 537,515, filed May 26, 1944, my application Serial No. 737,647, filed March 27, 1947, and an application of R. C. Jones, Serial No. 741,914, filed April 16, 1947, all assigned to the-Westinghouse Electric Corporation.

Heretofore, linear-motor catapults have been utilized for plane-launchings, for assisting the plane during its accelerating-run, for shortening the necessary length of the accelerating-run, thereby making it feasible for the plane to take ofi from a small landing-field; In general, as a practical matter, it is necessary, or highly desirable, to make it possible for-the plane to land at the same field from which it takes off; Since the landing-speed is practically the same as the takeoff-speed, it will be necessary to decelerate the plane, on landing, at a fair rate, which is somewhat less than the rate at which it was accelerated during takeoff, the reduced decelerating rate being permissible because of the possibility of utilizing the entire" length of the runway for the landing-operation, without the necessity for subsequently stopping and controlling a rapidly moving shuttle-car, as is necessary after a planelaunching operation.

In general, the problem of' arresting motion is not as difiicult as the problem of imparting motion to a heavy body, but there nevertheless remainsthe problem of providing a feasible means for obtaining an assisted deceleration of aplane after it has landed.

The problem of a plane-landing catapult, or a' plane-landing use of a' plane-launching catapult, is principally a problem of providing a suitable automatic control. An automatic controllingmeans is necessary, because of the extremely highlanding speeds of planes, the large masses involved, and the necessity for approximately matching the catapult-speed with the plane:- speed, and causing the plane to overtakethecatapult-car at a particular instant, or ata. particular point on the field, with a fair degree of accuracy. These requirements require split-second timing, which makes automatic control practically a necessity.

The general object of my invention is to provide a plane-landing catapult-assembly, with suitable automatic electrical control.

With the foregoing and other objects in view, my invention consists in the circuits, systems,

operations, combinations, apparatus and parts hereinafter described and claimed, and illustratedin the'accompanying drawing, wherein:

Figure 1 is a diagrammatic prospective view, not to scale, showing a portion of a landing-fiel lequipped with myelectrically controlled catapultcar'for reducing the length of the landing-run of an airplane which is landing at that field, and

Fig. 2 is a simplified schematic view of circuits and apparatus illustrative of the general nature of a suitable automatic electrical control for the catapult-car, 0r shuttle-car, as it is commonly called.

In Fig. 1, I show a plane I, which is about to land on a field 2 which is provided with an electrical linear-motor catapult which is represented by a shuttle-car 3, operating on a trackway-system which is diagrammatically represented by a single line 4, in Fig. 1. The shuttlecar 3 is shown as standing at its starting-point, ready for a plane-landing operation. To assist the airplane-pilot in landing, the field is marked with a landing-line 5 extending back of the starting-point of the car v3 on the trackway 4, and the field is also marked with a cross-line it, to indicate the point where the pilot should try totouch the runway, on landing. This landing-point should be some feet or 200 feet, or other suitable distance, back of the starting-point which is represented by the position of the shuttle-car 3 in Fig. 1.

At or somewhere near the landing-point, which is at the intersection of the field-markers. 5 and. t, I provide a plane-detector l, which is preferably sunk into the field, as diagrammatically indicated in Fig. 1. This plane-detector may beof any suitable type which. will detect the presence or near-approach of an incoming plane. Suitable detectors for this purpose would include a proximity-fuse, which operates on the principle of radio-wave reflection, or a photoelectric cell, which operates on the principle of light-rayreflection; or the plane-detector may be any other sort of device which will operate as a switching-means or relay PD which will respond to the approach or passage of the incoming plane I.

In Fig. 2, the shuttle-car 3 is represented, at

and carried b the shuttle-car 3. The secondary winding of the motor extends along the track- Way 4, and is not indicated in detai1 in either Fig. 1 or Fig. 2. In Fig. 2, the trackway 4 is diagrammatically shown somewhat more in detail than in Fig. 1, and it is shown as comprising a track The first line Ll of the diagram shows the use of the plane-detector make-contact PD, in series with three break or back-contacts 24, 2'5 and 25 of the two track-relays Tr7c! and Trk 2, and an auxiliary time-delay relay TX! respectively. These four serially connected contacts PD, 2d, 25 and. 26 are utilized to energize a landing-initiating circuit, from the positive bus to a conductor 2'5, which energizes the actuating-coil of a landing-control relay LC, the func- PBX, and three motor-feeding buses BI, 32' and B3, of which the buses B2 and B3 are third-rail buses. extending along the -trackway. while the bus BI is connected, as shown 'to the track TRK, by means of a plurality of feeder-connections 20, located at a plurality of spaced points 8, In, etc., along the trackway. These feeder-connections 2!! are equipped with current-transformers CT--' 8. CTHI, etc, which are utilized to energize either one of two track-relays Tr7cl and Trk-Z,

under the control of a position-selector drum 2!, as more particularly described and claimed in the R. C. Jones application, Serial No. 537,515.

Only the first four positions of the distanceselector drum 2| are shown, this drum being utilized for the purpose of preselecting a particular one of the current-transformers CT to be connected to the operating-coil of one of the trackrelays Trk-l or Trk-Z, and for also, as a safetymeasure or backup-protection, connecting the next succeeding current-transformer CT to the actuating-coil of the other track-relay. so that it can operate in case of failure of the first one. In each position of the drum 2|, all of the remaining current-transformers CT are short-circuited. These current-transformers CT become energized only when the shuttle-car is in a trackposition close to the location of the feeder-connection 20 in which the particular current-transformer-is located, so that the current-transformers are responsive to the position of the car on the track, during the accelerating-run of the car.

The three terminals of the primary motorwinding M of the shuttle-car 3 are at all times connected to the track TRk, the third-rail bus B2, and the third-rail bus B3, respectively, by means of current-collector shoes-22.

In Fig. 2, the power-plant is diagrammatically represented, in its barest essentials, b means of a three-phase generator AC-GEN, and a. constant-voltage direct-current energy-source or sources which are schematically represented by positive and negative bus-terminals (-1-) and The polyphase generator AC-GEN is provided with polyphase output-terminals Tl, T2 and T3, and it is also provided with a field-windine 23.

The simplified schematic diagram of Fig. 2 shows eleven across-the-line circuits, numbered L! to LI I, respectively, for the various controlapparatus, all of which is shown, for the purpose of simplification, as being connected across the) same direct-current bus-terminals and In the diagram, the various relays or electrically operated switches or .contactors, are suitably indicated by letters or legends, and these letters or legends are applied both to the operating-coils and to all of the contacts of any particular relay or switch, and in addition, arrows or dotted lines are used as a convention for Sy bolically tying together the various parts of any given relay or switch. The switches are all shown in their non-actuated positions.

tion of which is to initiate the energization of the automaticlanding-control mechanism, and to maintain its energization until the complete sequence of a plurality of predetermined automatic operations has been carried through to completion, as will be subsequently described.

- The second. line L2 of the diagram shows that the actuation of the landing-control relay LC immediately closes its make-contact 28, which energizes a conductor 29 having two branch-circuits. The first branch-circuit of 29 includes the back-contacts 38 of aNo. 4 auxiliary time-delay relay TXQ, which is connected to the energizingcircuit 27 of the landing-control relay LC. The circuit 282930 thus operates as a holdingcircuit for the landing-control relay L0.

The second branch-circuit of the conductor 29 contains the threev serially-connected back-contacts 3!, 32 and 33, of the two track-relays Trk I and Tris-2 and the-No. 1 auxiliary time-delay relay TXI, respectively, and these three serially connected contacts are utilized to energize a circuit 34, which continues on, through two serially connected back-contacts 35 and 36 of a braln'ngrelay or contactor Blcg and a reverse-relay or contactor R, respectively, to energize a conductor 31 which energizes the actuating-coil of a forward-contactor F.

The forward-contactor conductor 31 has a branch-circuit containing a make-contact 33 of said forward-contactor F, which continues on, through a back-contact 39 of a field-switch Fld, and a make-contact 40 of the landing-control relay LC, to energize a conductor 4! which energizes the actuating-coil of the field-switch Fld. The field-switch conductor M has a branch-circuit containing a make-contact 42 of the landing-control relay LC, which is utilized to immediately energize a No. 2 field-resistance relay FldR2. The energization of the field-switch Fld closes its make-contact 43, which bypasses its back-contact 39, thus establishing a holding-circuit for the field-switch Fld. The make-contact 43 preferably closes before the back-contact 39 opens.

The landing-control energizing-circuit M has a branch-circuit M, containing three parallel-connected make-contacts 45, 46 and ll of the two track-switches Trk-l and Trk-2 and theNo. 1 auxiliary time-delay relay TXI, respectively, and these three contacts are utilized to energize a circuit 48 containing two serially connected backcontacts 49 and 50 of the forward-contactor F and the field-switch Fld, respectively, to energize a conductor 5! which energizes the actuatingwinding of a braking-contactor Bkg. The braking-contactor circuit 5! has a branch-circuit containing a make-contact' 52 of a No. 2 auxiliary time-delay relay TX2, which energizes a conductor 53 which energizes a N0. 1 braking-resistance relay B7cgR.l. The conductor 53 has a branch circuit containing a back-contact 5A of a No. 3 auxiliary time-delay relay TX3, for energizing the actuating-coil of a No. 2 braking-resistor relay BlcgR2.

The; foregoing connections complete themain relay-coilconnections; for anlautomatic landingopcration, including an, initial polyphase-power accelerating-run, under the control of the forward-contactor E, followed: by a direct-current braking-operation; under the control of;the brakingecontactor Blag, the; operation of which will be subsequently pointedout in detail; At the conclusion of thisautomatic operation, theshuttle-car- 3:, Q1:M"..will be left either standing; still or operating atarel'ativelyslow "speed. In either event, inordertodisconnect the shuttle-car from the: plane whichitwis; assistingit is necessary to move the shuttle-car forward again, ahead of the plane, orto make the plane drop back, for a sufiicientdistance toenable the pilot to turn the; plane and move itv off of, the runway, after which the shuttle-car may be brought back, usually under manual control, to its starting-position, to, getzit in position for another plane-landing operation.

The; third line L3. of the schematic diagram shows; a circuit containing .a back-contact 55 of the landing-control relay LC, to energize a conductor56iwhich is utilized for serving a spottingswitch- SS, which performs the slow-return functions ofthe main controller-switch of the Powers patent, orthe-spotting-switch functions of the R.-

C; Jones application, Serial No. 537,515. As de-- scribed. and claimed in: the R. C. Jones application, Serial No. 7413914, this spotting-switch SS can not be utilized except when the operationcontrolling, or landing-controlling, relay LC is in its deenergized position, wherein its backcontact. 55 is closed;

The spotting-switch SS has two forward-positions, designated by the suffixes FI and F2, and tworeverse-positions, designated by the suffixes R1: and: R2, there being several switch-contacts in each. of these four positions.

From the spotting-switch energizing-conductor 56, there are four branch-circuits. A first branch-circuit includes two parallel-connected make-contacts 51 and '58 of the two forward positions SS:F'| and SS-FZ of the spotting-switch, and these twocontacts are utilized toenergize the circuit 36?-35 36- 3T which energizes the forward-contactor F. A second branch-circuit of the concluctor-56includes two parallel-connected make-contacts 59 and 60, which are closed in the two reverse-positions SS-Rl and SS--R2- of the spotting-switch. SS. and these two contacts are utilized to energize-a conductor 51 containing two serially-connected back-contacts 62' and 53 of the braking-contactor-B'kg and the forward-contactor respectively, to energize the actuatingwinding of the reverse-contactor R. A third branch-circuit of the conductor 56 includes four parallel-connected make-contacts 64, 65, E6 and 61, which, areclosed. in all four positions SS---F'l, SS-.F2; SSR! and SS-'R2= of the spotting switch SS, these four contacts are utilized to ener ize the energizing-circuit conductor 4| of the field-switch Fld: A fourthbranch-circuit ofthe conductor 56; includes, two parallel-connected make-contacts 58' andv 69 which are energized in the No. 2, forward and reverse positions SSFZ and SS -R:2:0fthe spotting switch SS, and these two, contacts are utilized to energize acircuit containing a back-contact H of the landingcontrol relay LC, to energize the actuating-coil of the No. 1 field-resistance relay Fld-Rl.

The fourth line L4 of the schematic diagram shows the use of a reset-pushbutton, marked Reset-1R3, in a circuit containing a-serially-connected: beanie-contactv 12 of: the landingwontrol relayaLQto energize three reset-coils ofthe two track-relays Trkl and Tris-4, and the: No., 1 auxiliary-tirne-delay relay TXI The three reset-coils arev designated by the legends Reset- Trial; Resete-TrkZ- and Reset--TXI. These three relays Trkl, Tr-lc--2' and TXI are position-retainingtrelays, which remain in their actuated positions, once they are. momentarily actuated, until they reset by a momentary energization of their. respective reset-coils;

The fifth line L5 of the schematic diagram shows the energization' of an inverter 13, which supplies; alternating-current voltage, of any suit.- able frequency, to four alternating-current timers, or time-delay relays, TDI to TD4, which are utilized to time the accelerating-run and the various portions of the direct-current brakingoperation. The first timer 'ID'l is actuated,v or set "in motion, by a make-contact 14 of the forwardi-contactor F, while the second, third and fourth timers. TD2i, TD3 and TD4 are respectively actuated, or set in motion, by the makecontacts 15, I6 and T! of the'braking-contactor Bkg, a No. 2 auxiliary time-delay relay TXZ; and a No. 3 auxiliary time-delay relay TX3, respectively.

The sixth line L6; of the diagram shows that the first timer TDI has a make-contact 18 which energizes the No. 1 auxiliary time-delay relay TXI, this relay being a position-retaining relay, as previously explained;

The lines L1, L8 and. LQLOf the schematic diagram show the use of three parallel-connected make-contacts 19, and 8'! of the two trackrelays.Trkland Trk2 and the No. 1 auxiliary time-delay relay TXI, to energize a circuit 8IA, having several branch-circuits, which energize the actuating-coils of the No. 2, No. 3 and No. 4 auxiliary time-delay relays TXZ, 'IXS and TX4, respectively, through the respective make-contacts B 2, 83 and B4 of the correspondingly numbered timers TDZ, TD3 and TD4, each controlling its own auxiliary time-delay relay. Each of these auxiliary time-delay relays TX2, TX3 and TX4', whenever energized, immediately seals itself, in, through a make-contact 82., 83' or 84-, as the case may be, bypassing the corresponding timer-contacts B2, 83 and 84, respectively.

The tenth line LID of the schematic diagram shows the use of two make-contacts 85 and 86 of the field-switch Fld for energizing the fieldwinding 23 of the alternating-current generator AC-GEN, across the direct-current terminals and through a field-resistance 81, various portions of which areshort-circuited by the make-contacts 88 and 89 of the respective fieldresistance relays FloZ'--Rl and FZdR2. The generatorfield winding 23 is preferably bypassed by a field-discharging resistor 9!].

The eleventh line Lil of the schematic diagram shows how the make-contacts 9i and 9 2 of the braking-contactor Bkg connect two of the track-system buses BI and B3, respectively, to the positive and negative terminals(+) and respectively, through a current-limiting brakingresistance 93" and. a choke-coil 94. Various portions of the braking-resistance 93 are short-circuited bythe make-contacts 95 and 96' of the respective braking-resistance relays BkgRl and Bkg-RZ, thus controlling the amount of braking-energy. The-ohoke-coil 96 serves to limit the rate-ofrise ofthe direct-current in the brakingcirouit, when thebraking-contactorBlcg is closed;

7 thus protecting the direct-current bus and from having too sudden a load thrust upon it. 7

The switching equipment of my automatic control-system is completed by the main contacts 91 and 98 of the polyphas-e contactors F and R, which apply the polyphase power of the generator-terminals Tl, T2 and T3 to the motor-circuit buses Bl, B2 and B3, in either the forward or reverse phase-sequence, respectively.

As shown in Fig. 1, suitable shock-absorbing engagement-means or coupling-means are provided, for cushioning the overtaking-contact of the plane with the accelerated car on the landing-field. This coupling-means may take any one of a number of difierent forms, and is diagrammatically indicated as including a dependinghook I00, in the rear portion of the underside of the plane I. When the plane overtakes the shuttle-car 3, the hook H engages a transverse cable lill, which extends between pulleys "32 on the car, the ends of the cable being anchored in oleo shock-absorbers I03, which may yield a number of feet in length, while enabling the plane and. the car to adjust themselves for any small initial difference in their speeds at the moment of contact. This shock-absorbing planeengaging means may be arranged, if desired, for quick installation and removal on the shuttlecar 3. It will be understood that the transverse bight-portion of the cable [M will be disposed about one or two feet, or other suitable distance, above the top of the shuttle-car 3.

In the operation of my invention, when a plane is about to come in, to the landing-field 2, for an assisted landing, the operator in the powerplant will be given advance-notice of the landing-speed of the plane, and he will set up the controls, accordingly, so as to apply the correct amount of power, or the full power, to the shuttlecar motor M, for the correct length of time, or' for the correct distance along the trackway 4, to accelerate the car to a speed a little less than the speed of the plane which is about to land. The timing should be such that the plane will overtake the shuttle-car at about the instant when the accelerating power is cut off, or a second or so, or a fraction of a second, thereafter.

The power-plant operator makes these adjustments with the aid of charts or tables (not shown) which enable him to set the distance-selector drum 2i so as to cut off the power when the car reaches the proper point along the trackway. This distance-selecting adjustment, for presetting' the length of the accelerating-run of the shuttle-car, can be utilized, either with full powerapplication to the shuttle-car, or in conjunction with any one of several charted adjustments of the amount of field-resistance 81 which is cut out'by the No. 2 field-resistance relay FZd-R.2, as indicated at I04 in line LIB of Fig. 2. As a backup protective-means, the power-plant operator also sets or adjusts the timing of the No. 1 timer Tdl, to out 01f the accelerating-power, at a time, as shown on his charts, such that the attained car-speed would be only very slightly larger than if the accelerating-run had been terminated by one of the track-relays Trlclor TrIc-'-2 which are associated with the distanceselector drum 2|. This afiords protection, even though the track-relays should both fail.

*If there is a wide margin of difference in the weights of the various planes which come in to the field for assisted landings, the power-plant operator may also secure advance information 8 of the weight of the incoming plane, by which he may adjust or preselect the time-settings of the three braking-controlling timers TD2, TD3 and TD l, or he may preselect the final amount of the braking-energy, in the third or final stage of the braking-operation, by adjusting the amount of the braking-resistance 93 which is cut out by the No. 1 braking-resistance relay Blcg-Rl, as indicated at I05 in line Ll I of Fig.2.

The initial power-plant presettings or adjustments, in readiness for an incoming plane, will be better understood when the'sequence'of the landing-operation has been traced to its conclusion, as will now be done.

The pilot of the incoming plane will line up along the continuous straight line 5-4 on the landing-field 2, and will try to touch the runway approximately on the spot indicated by the crossline marker 6 on the runway.

Approximately at the instant when the plane makes landing-contact with the field, the planedetector '5 responds, and closes its PD contact,

in the first line, Ll, of the schematic controldiagramj This operation automatically sets in operation a complete sequence of electrical control-functions which perform a predetermined sequence of control-operations, and carry them through to completion, without the control of the operator, other than the set of pre-setting adjustments such as those which have already been described, or any other set of presetting control-adjustments which may be desirable.

' The momentary closing of the plane-detector contact PD, in line Ll 'of Fig. 2, energizesthe operation-controlling or landing-controlling relay LC, which immediately locks itself in, through a holding-circuit 28-293ll'-21, which remains closed until the complete landing-operation has been finished, as indicated, in the illustrated form of embodiment, by the opening of the back-contact 30 of the last auxiliary timedelay relay TX4.

The actuation of the landing-control relay LC immediately energizes the 'forward-contactor F, through the circuit from 29 through 3! to 31; and the completion of the response of the forward contactor F immediately energizes the fieldswitch Fld, through the circuit from 31 to 38 through 4|, and at the same time, the No. 2 fieldresistance relay Fld''-R2 is energized through the circuit 41-42. These operations cause the poly phase generator AC-GEN to be connected to the car-serving buses Bl, B2 and B3, through the iorward-phase-seque'nce contactor-contacts 91, at a time when the generator is unexcited, and hence when its voltage is very low. Immediately, however, exciting-energy is applied to the gen-- erator field-winding 23, and the field-flux begins to build up,'in the generator, at a rate which is determined by the time-constant of the generator, and by the voltage and resistance-conditions of the field-energizing circuit which is line Li (I of the schematic diagram. The generator-field, and hence the generator-voltage, thus builds up smoothly, but rapidly, so as to apply the accelerating-power to the shuttle-car 3 or M, without too great shock on the power-plant or'the forward-contactor F; Before the car has moved very many feet, the full power (or any other preselected power) of the generator AC-GEN will be applied to the car.

The accelerating-run of the shuttle-car is normally interrupted by the operation of one of the track-relays Tris-l or Trk2, which opens its back-contact3l or- .3 as the case may be, in

the energizing-circuit of the forwardicontactor' F and the field-switch Fld. At the same time, the track-relay closes its make-contact 45 or in the energizing-circuit A l-| of the braking contactor Blcg, and as soon as the forward-contactor F and the field-switch Fld are fully opened, their back-contacts 49 and 50. will complete this energizing-circuit for the braking-contactor Bkg.

While I have shown thethree parallel-cone nected make-contacts 35, t6 and 3'! as automaticrelay contacts, of the relays Trkl,. ,Trk--2 and TXI, for energizing the braking-contactor Bkg.

and initiating the braking-operation of the shuttle-car, I wish it to beunderstood that I, am"

not limited to these precise contacts or relaymeans; as the braking-operation could be initiated either manually, or by. any other automatically responding control-means. The essential thing is that the braking-operation should be initiated, manually or automatically, either just as the plane is approaching towardits overtaking-contact with the shuttle-car, or: aslsoon after such contact as is reasonably convenient. The contact-making act, between the plane and the car, may be visually observed by an operatorv or by a light-sensitive relay (not shown) placed to one side of the runway, or said act may be responded to by signalling apparatus (not shown) on the plane or the car, and thesignal may be discontinuance of the accelerating-power, it.

should be understood that my invention is not limited to this immediate application of the braking-power, immediately after the discontinuance of the full accelerating-power, but a timedelay interval may be interposed, either by completely cutting off the forward acceleratingpower, waiting an interval and then completely applying the full braking-power, or by first reducing the accelerating-power to a very small amount, before finally cutting oif the accelerating-power and then instantly applying the braking-power, or by suddenly cutting off the full accelerating-power, and instantly applying avery small braking-power, which is left onfor a predetermined time-interval, before applying. the full braking-power. I have chosen to illustrate the third alternative, under the control of the No. 2 timer TD2, and this illustration is intended to be representative of any suitable means-for introducing a time-interval, according to the timesetting of the No. 2 timer TD2, during which the speed of the shuttle-car is not changing very greatly, either by way of acceleration or deceleration. provide a certain factor of safety in regard to the predetermination of the precise point in the landing field, or the precise instant of time, at

which the plane I overhauls the shuttle-carv 3;

In the form of embodiment whichI now prefer,

as shown in Fig. 2, the energization of thelbrakiing-contactor circuit 44 5l applies direct-current braking-power to the shuttle-car, with the full amount of the braking-resistance 93 incir-- cuit, as shown in the line LII of the schematic diagram. The value of this braking-resistance- This expedient is desirable, in order to.

10. 93 may be such thatthebrakingepower which is applied to the shuttle-car during. this portion of the operating-sequence is very small, merely enough to help to hold rthecontacting-cable l'lll taut, when thevplaneh'ook I00 first engages the same.

Here. again, the apparatuszwhich I have chosen for illustration is intended to bezsymbolic, in a broader sense,- of, any suitable or. equivalent means for performing a braking ordecelerating function,.by;means-of any suitable electrical energizati-on of theshuttle-car which will result in reducing its speed. Such'braking-energization of the shuttle-car would include; in its broadest range of equiva'lentsg the application of reversephase-sequence p'olyphase: power, for plug reversal, asin-the-Powerspatent, or the application (as shown) of direct-current power to two or more of the phases or phase-terminals of the polyphase shuttle-car motor M.

After-the expiration of the time-settin of the No. 2 timer TD2, the No; 2 auxiliarytime-delay relay TXZ is energized, and closes its make-contact 52 in the energizing circuit 5l52-53 of the two braking-resistance relays B7cg-l=tl and Bing-R2, thuscutting out nearly all of the braking-resistance 93,- and applying the full amount of braking-powerwhich therapparatus will safely stand, or any other desired amount of brakingpower.

After a predetermined time-interval, after the energization of the-Nd 2: auxiliary time-delay relay TXZ; the No. 3:timer TD 3-zcloses its contact 83 and energizes the No. 3 auxiliary timet delay relay TXB which immediately opens its back-contact 54 and deenergizes theNo. 2 braking-resistor relay Bkg,R2. The opening of the relay BkgR2r puts back; in the braking-circuit LI I, some of the braking-resistance 93. This operation should preferablybe timed so as to occur at some time when the speed of the shuttle-car, and'hence .the. speedof theplane, has been reduced to some small amount, but has not been brought to standstill.

The amount of braking-energy which is thus finally applied to the car, after the operation of the No. 3 ti'mer T133, willthus be reduced, so as to lessen the-jerk with which the car might otherwise be stopped, as .will be readily understood. While only a singli stage. of brake-reducing power is shown, it will be readily, understood that a multiplicity of such stages might be utilized, if desi-redI. The problem. of smooth-stoppin may not mak'eit necessary to utilize more than one, if

any, brake-reducing, stage, because of" the fact that the eifectiveness of the direct-current energization of some or all .of. the polyphase windings of a squirrel-cage motor is a tunction of the speed of the motor, so that the braking-pull or force inherently falls oiirapidly when the speed of .the shuttle-car ,is reduced, even without any reduction in. the direct-current braking-energy, as by-the opening. of the No. ZIbraking-resiStance relay Blew-R2,

However, even though theresistance-introducing step-corresponding to theopeningotthe TXS back-contact 54-is not needed from the standpoint of securing a smooth: stopping, without any final jerk, because of the inherent falling-offerbecauseor therincraeased magnetieflux which a.

given-a-braking-current produces as the shuttle- I1 car "(audits motor) approachesstandstillj 'When an' induction-motor=is moving at a reasonable speed, while its primary winding M is excited with a direct current, .the unidirectional flux, in the'primary winding; cuts the squirrel-cage (or other) secondary winding (in this case stretched out along the tra-ckway) ,sothat the induced circulating current, in the secondary winding, bucks down the primary-winding flux. When the motor stops, or nearly stops, the primary-winding flux reaches its full magnitude. Now, in an ordinary circular motor, this phenomenon would not be very important, but in a linear motor, as in my catapult, the magnetic flux produces a very considerable magnetic pull between the shuttle-car 3 and the track-structure 4. The necessity for keeping down the final amount of flux, which appears wh'en the motor (or shuttle-car) approaches standstill, so as to limit the mechanical bending of either the car or the trackway, imposes a definite limit on the amount" of braking current which may be permitted to fiow in the primary winding M when the shuttle-car speed is reduced to zero. Hence, theemployment of the resistance-introducingstep corresponding to the opening of the 'IX3 back-contact 54 before the carspeed is reduced to too low a-value, makes it possibleto use more braking-power while the car is in fast motion, without mechanically overstressing either the caror the trackway.

Aftera predetermined time-interval after the actuation of theresistance-introducing step 54 by the'energization of the No. 3 auxiliary timedelay relay TXS', the "last timer TD4 operates, energizing the 'No, 4 auxiliarytime-delay relay TX l, and causing it to open its back-contact 30 in the, holding-circuitof the landing-control relay LC, and at the same time deenergiz'ing the brakingcontactor energizing ciricuit 44 5l.

This No. 4 time-delay setting would usually preferably be set so that the sjhuttle-car (and the plane) will have been brought to standstill, with an additional time added, for a reasonable factor, of safety,,before the braking-circuit LII is deenergized, thus finally relieving the power-plant of an'unn ecessary power-drainage,relieving the shuttle-car motor-Winding M of unnecessary overheating and releasing the shuttle-Carin readiness for further 'polyphase 'energization and control, as will be subsequently described.

However, as previously intimated, it is possible to operate my systemso that No, 4 timer TDl interrupts the direct-current braking-circuit before the car and the plane have come to a full stop, being merely reduced to a reasonably slow and readily controllable speed, after which the car would be left to run ahead, either coasting without polyphase propelling power, or withv the application of a small amount. of forward phasesequence polyphase-power, either manually or automatically applied, while the pilot of the plane would apply his own brakes and cause the plane to detach itself from the shuttle-car couplingcable It], after which the pilot could turn the plane and move it on of the runway in the ordinary manner. The shuttle-car could then be brought to dead standstill, -either automatically I or by manual control by the use of the spottingswitch SS.

After the shuttle-car has been brought to standstill, by whatever braking-power means is utilized, the car can then be controlled by the spottingswitch SS, by means of which the operator can 7 move the car'either forward or backward,'with either one of two different amounts of polyphase voltage,according asthe first or second spotting- 1 switch position is utilized, in either the forward or i reverse direction. By this means, the shuttlecar can be disengaged from the plane-hook Hill (if it is not alreadydisengaged), and after the' gization of the reset-pushbutton Reset-PB, in

line L4 of the schematic diagram.

While, in the foregoing explanation, I have de scribed only the plane-landing functions of a catapult, and while I have shown only the planelanding control in the drawing, it is to be under- I stood that the same shuttle-car, track, and powerplant may be used also for plane-launchings, with suitable modifications in the control-circuits and the coupling-attachments.-

While I have illustrated my invention in an exemplary, and at present preferred, form of embodiment, I Wish it to be understood that my invention is of rather broad application, represent mg broadly new principles of operation and con- 3 trol, and I desire that the appended claims shall be understood as embracing a suitable range or equivalents in regard to the precise means and operations which are employed.

I claim as my invention:

1. A plane-landing catapult-assembly for re ducing the length of the landing-run of an airplane which is landing at a landing-field, said catapult-assembly comprising: a self-propelled, electrically energized car, initially standing at a predetermined starting-point in the field; accel erating-means, including an electrical energysource and control-means, for providing an automatically controlled electrical accelerating-energization for the car; means for presetting the accelerating-operation; decelerating-means, in-;

cluding an electrical energy-source and controlmeans, for providing an electrical decelerating energization for the car; plane-detecting means,

back of said starting-point in the field, for detectmg the landingapproach of a plane at a predei termined detection-point back of said startingpoint; means responsive to said plane-detecting means for automatically initiating said accelerating-operation; shock-absorbing coupling-means for cushioning the overtaking-contact of the.

plane with the accelerated car on the landingfield; and meansfor initiating the deceleratingoperation,

2. A plane-landing catapult-assembly for reducing the length of the landing-run of an airplane which is landing at a landing-field, said catapult-assembly comprising: a self-propelled,

electrically energized car, initially standing at a predetermined starting-point inthe field; accelcrating-means, including an electrical energysource and control-means, for providing an automatically controlled electrical accelerating-energization for the car; means for presetting the accelerating-operation; decelerating-means, in-, cluding an electrical energy-source and controlj means, for providing an automatically controlled 1 electrical decelerating-energization for the car;

means for presetting the decelerating-operation;

plane detecting means, back of said startingpoint in the field; for detecting the landing-ap'-' proach of a plane at a predetermined detectionpoint back of said'starting-point; means responsive to said plane-detecting means for automatically initiating said accelerating-operation; shock-absorbing coupling-means for cushioning the overtaking-contact of the plane with the accelerated car on the landing-field; and'means for initiating the decelerating-operation;

3. The invention as defined in claim 1, in combination with supplementary control-means for subsequently electrically" energizing the car to return the car to a desired starting-point ready for another plane-landing operation.

4. The inventionas defined: in Clad I112; in combination with supplementary control-means for subsequently electrically energizing the car to return the car to a desired starting-point ready for another plane-landing operation.

5. A. plane-landing catapult-assembly for retiming the length of the lan'ding run of an airplane Which is landing at a landing-field, said catapult-assembly comprising: a self-propelled, electrically energized car, initially standing at a predetermined starting-point in the field; accelerating means, including an electrical energysource and control-means, for providing an automatically controlled electrical accelerating-energization for the car; means for presetting the accelerating-operation; decelerating-means, including an electrical energy-source and controlmeans, for providing an automatically controlled electrical decelerating-energization for the car; means for presetting the decelerating-operation; plane-detecting means, back of said starting point in the field, for detecting the landing-approach of a plane at a predetermined detection-point back of said starting-point; means responsive to said plane-detecting means for automatically initiating said accelerating-operation; shock-absorbing coupling-means for cushioning the overtaking-contact of the plane with the accelerated car on the landing-field; and means responsive to the termination of the accelerating-operation for automatically initiating the decelerating-operation.

6. The invention as defined in claim 5, in combination with supplementary control-means for subsequently electrically energizing the car to return the car to a desired starting-point ready for another plane-landing operation.

'7. A plane-landing catapult-assembly for reducing the length of the landing-run of an airplane Which is landing at a landing-field, said catapult-assembly comprising: a polyphase-motored shuttle-car, initially standing at a predetermined starting-point in the field; a trackway for said shuttle-car in the landing-field; a polyphase motor-energizing bus-system which is continuously connected to said polyphase-motored shuttle-car; accelerating-means, including a polyphase energy-source and control-means, for providing an automatically controlled electrical accelerating-energization for the motor-energizing bus-system; means for presetting the accelerating-operation of the shuttle-car; decelerating-means, including an electrical energy-source and control-means, for providing an electrical decelerating-energization for the motor-energizing bus-system; plane-detecting means, back of said starting-point in the field, for detecting the landing-approach of a plane at a predetermined detection-point back of said startingpoint; means responsive to said plane-detecting means for autornatically initiating said' accelerati ing-operation; shock-absorbin .v coupling-means for cushioning the overtaking-contact of' the plane with the accelerated car on the landingfield; andmean for initiating the deceleratingoperation.

8. The invention as defined in claim Lin combination with supplementary control-means for subsequently electrically energizing the car to return the car to a desired starting-point ready for another plane-landing operation.

9. A plane-landing catapult-assembly for retiming the length of the landing-run of an airplanewhich is landing at a landing-field, said catapult-assembly comprising: a p0lyphase-mo-' tored shuttle-car, initially standing at a 'predeter'mined starting-point in the field; a trackway for said shuttle-car in the landing-field; a polyph-ase-motor-energizing bus-system which is continuously connected to said polyphase-motored shuttlecar; accelerating-means including a polypnase energy-source and control-means, for providing an automatically controlled electrical aceel'erating-energization for the motor-energizing bus-system; means forpresetting the accelerating-operation of the shuttle-car; deceleratingmeans, including an electrical energy-source and control-means, for providing an automatically controlled electrical decelerating-energization for the motor-energizing bus-system; means for presetting the decelerating-operation of the shuttlecar; plane-detecting means, back of said startingpoint in the field, for detecting the landing-approach of a plane at a predetermined detectionpoint back of said starting-point; means responsive to said plane-detecting means for automatically initiating said accelerating operation; shock-absorbing coupling-means for cushioning the overtaking-contact of the plane with the accelerated car on the landing-field; and means for initiating the decelerating-operation.

10. The invention as defined in claim 9, in combination with supplementary control-means for subsequently electrically energizing the car to return the car to a desired starting-point ready for another plane-landing operation.

11. A plane-landing catapult-assembly for reducing the length of the landing-run of an airplane which is landing at a landing-field, said catapult-assembly comprising: a polyphase-motored shuttle-car, initially standing at a predetermined starting-point in the field; a trackway for said shuttle-car in the landing-field; a polyphase motor-energizing bus-system which is continuously connected to said polyphase-motored shuttle car; accelerating means, including a polyphase energy-source and control-means, for providing an automatically controlled electrical accelerating-energization for the motor-energizing bus-system; means for presetting the accelerating-operation of the shuttle-car; decelerating-means, including an electrical energy-source and control-means, for providing an automatically controlled electrical decelerating-energize.- tion for the motor-energizing bus-system; means for presetting the decelerating-operation of the shuttle-car; plane-detecting means, back of said starting-point in the field, for detecting the landing-approach of a plane at a predetermined detection-point back of said starting-point; means responsive to said plane-detecting means for automatically initiating said accelerating-operation; shock-absorbing coupling-means for cushioning the overtaking-contact of the plane with the accelerated car on the landing-field; and

' 15 means responsive to the termination of the accelerating-operation for automatically initiating the decelerating-operation.

12. The invention as defined in claim-11; in combination with supplementary control-means for subsequently electrically energizing the carv to return the car to a desired starting-point ready for another plane-landing operation.

13. In combination, a polyphase load-circuit supply-line, a polyphase energy-circuit supplyline, a direct-current energy-circuit supply-line, a polyphase motor constantly connected to said polyphase load-circuit supply-line, alternatingcurrent-controlling means operable only when said direct-current energy-circuit supply-line is disconnected and comprising a main startingcontactor for energizing said polyphase load-circuit supply-line from said polyphase energy-circuit supply-line inthe one phase-sequence or the other for a forward run of said polyphase motor,

means for opening said main starting-contactor for terminating said forward run, direct-currentcontrolling means operalgle only when said polyphase energy-circuit supply-line is disconnected and comprising a braking-contactor for energizinga plurality of conductors of said polyphase REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,131,610 Arndt Sept. 27, 1938 2,380,105 Gerrard July 10, 1945 FOREIGN PATENTS Number Country Date 470,767 Great Britain Aug. 20, 1937 

